1. Field of the invention
The invention relates to the field of power electronics.
It proceeds from a circuit arrangement or from a power semiconductor module in accordance with the preamble of the corresponding independent claims.
2. Discussion of background
European Patent Application EP-A2-0 417 747 has already described such a circuit arrangement or such a power semiconductor module.
In that case, the circuit arrangement comprises at least two power semiconductor switch modules having a package, two main connections and two gate connections. The power semiconductor modules used are constructed correspondingly.
A module comprises, as a rule, a plurality of semiconductor components which can be combined to form a logic functional unit. Examples are rectifiers, individual switches comprising antiparallel diodes or entire phase assemblies. Such modules (thyristor, transistor, IGBT, diode modules) are nowadays widespread in the power region of 1,200 V and a few 100 A and are primarily used in industrial drives.
In order to obtain a required performance, a plurality of components of one type are, as a rule, connected in parallel in one module. Thus, for example, each IGBT half-bridge module for 150 A, 1,200 V may contain six parallel-connected IGBTs and two parallel-connected antiparallel diodes per switching function.
At present, upper limits are imposed on the performance of modules (in particular in relation to current carrying capacity) since modules cannot be constructed with any size desired. The difficulties lie in the reliability problems, which increase considerably with the overall size, and the parallel connection of a large number of components, which becomes increasingly more difficult.
In addition, with increasing size of the modules, one of their outstanding characteristics is lost, namely the modularity, i.e. the increase in the electrical power not through ever larger components but by connecting ever more similar components in parallel. For these reasons, the unlimited connectability of modules in parallel would be a desirable characteristic.
Unfortunately, limits are imposed on the connectability of modules in parallel. Since, after all, the electrical parameters of the modules are never quite identical, the forward, reverse and switching behavior of the modules may be different. In the case of parallel connection, this may result in oscillations or overloading of individual modules until they are destroyed. The publication mentioned at the outset attempts to counteract this by attempting to reduce the inductance of the commutating circuit by means of a special arrangement of the electrodes.
However, this does not take account of the abovementioned problems, which are due to parameter differences. As a rule, this problem is solved by preselecting the modules to be connected in parallel in relation to critical parameters. As a result, it later becomes virtually impossible in the application to replace a single module in a parallel circuit. A further possibility is that the modules are not exploited up to their specified performance ("derating").
In a new category of modules, the so-called integrated or intelligent modules (integrated power modules, IPM), additional functions, such as triggering of the components to be switched, logic for recognizing faults (e.g. excess temperature, overcurrent, undervoltage of the supply) and electrical isolation of the triggering and fault signals are incorporated in the module.
Added to the problems described above in the case of the parallel connection of such modules, which parallel connection is required for high powers, are those of the triggering, fault detection and fault processing, etc. which do not function precisely simultaneously.
Thus, for example, a slight variation in the voltage supply of the receiver of an optical waveguide used for the potential-free transmission of the triggering signal and incorporated in the module may result in a propagation time delay of a few 100 nsec, which has a considerable adverse effect on the parallel connection of such modules.